Shock absorbing stop for fixed path vehicle

ABSTRACT

This is apparatus for positive stopping of a fixed path vehicle with a minimum of shock. The fixed path vehicle carries a pair of floating fluid type shock absorbers which are so located as to engage pairs of positive stops at each limit of travel of the vehicle to transmit a stopping force to the vehicle which is a function of vehicle velocity. The fluid shock absorbers are of the cylinder double-ended piston type in which restricted flow of fluid is permitted between the cavities on each side of the piston. The shock absorbing mechanism has a spring between the piston and cylinder biasing the piston into the extended position against fixed brackets on the vehicle. Fixed stops are mounted in the floor to limit the travel of the vehicle in each direction. When the vehicle travels in one direction into the stops, the piston end of the shock absorbing mechanism engages the stops while the cylinder end engages a bracket on the vehicle thereby transmitting force from the stop to the bracket, which force is a function of velocity. When the vehicle travels in the opposite direction against the stop at the other limit of travel, the cylinder engages the stop while the piston rod engages the opposite bracket on the vehicle thus transmitting force from the stop to the bracket which is a function of velocity of the vehicle. In this way, the same shock absorber is used for stopping the vehicle in both directions at the limit of travel. A pair of the shock absorbers may be mounted equidistant from the center of mass of the vehicle to exert the stopping force without excessive torque about an axis normal to the direction of travel of the vehicle.

United States Patent [191 Snyder et al.

SHOCK ABSORBING STOP FOR FIXED PATH VEHICLE inventors: James H. Snyder;William E.

Riedner, both of Battle Creek, Mich.

Assignee: Clark Equipment Company, Buchanan, Mich.

Filed: Dec. 8, 1971 Appl. No.: 206,223

[52] US. Cl 104/256, 105/392.5, 105/454, 213/8, 213/43 Int. Cl. B6llt7/18, 861g 11/12 Field of Search 2l3/8, 43, 223; 104/249-256; 293/30;105/3925, 454;

214/16 B; 49/360; l60/l87189, 202, 224

References Cited UNITED STATES PATENTS 7/1967 Smith 105/454 8/1967Peterson 105/454 12/1903 Dittbenner 104/256 5/1906 McCormick.... 104/256l/19l4 McDonald 104/256 Primary Examiner-Drayton E. Hoffman v A ttorney-Kenneth C. Witt, Lewis J. Lamn et a].

[5 7] ABSTRACT This is apparatus for positive stopping of a fixed pathAug. 28, 1973 vehicle with a minimum of shock. The fixed path vehiclecarries a pair of floating fluid type shock absorbers which are solocated as to engage pairs of positive stops at each limit of travel ofthe vehicle to transmit a stopping force to the vehicle which is afunction of vehicle velocity. The fluid shock absorbers are of thecylinder double-ended piston type in which restricted flow of fluid ispermitted between the cavities on each side of the piston. The shockabsorbing mechanism has a spring between the piston and cylinder biasingthe piston into the extended position against fixed brackets on thevehicle. Fixedstops are mounted in the floor to limit the travel of thevehicle in each direction. When the vehicle travels in one directioninto the stops, the piston end of the shock absorbing mechanism engagesthe stops while the cylinder end engages a bracket on the vehiclethereby transmitting force from the stop to the bracket, which force isa function of velocity. When the vehicle travels in the oppositedirection against the stop at the other limit of travel, the cylinderengages the stop while the piston rod engages the opposite bracket onthe vehicle thus transmitting force from the stop to the bracket whichis a function of velocity of the vehicle. In this way, the same shockabsorber is used for stopping the vehicle in both directions at thelimit of travel. A pair of the shock absorbers may be mountedequidistant from the center of mass of the vehicle to exert the stoppingforce without excessive torque about an axis normal to the direction oftravel of the vehicle.

8 Claims, 4 Drawing Figures mtmumsze ms 3.754 513 SHEET-1 0F 3 FIG. I

PAIENIEUmcza I975 SHEET 3 OF 3 R S RRE N W D Nmm ww w. .E H M 5 L mu JwY B A ON W wm vm ATTORNEY SHOCK ABSORBING STOP FOR FIXED PATH VEHICLEBACKGROUND AND SUMMARY OF THE INVENTION floats between two brackets onthe vehicle and in one direction of travel the piston end engages thelimit stop while the cylinder end engages the vehicle bracket and at theother limit of travel, the cylinder end engages the limit stop while thepiston end engages the second bracket on the vehicle.

Previously one shock absorbing means has been used to stop the vehiclein one direction of 'travel, while a second and independent shockabsorbing means has been used to stop the vehicle travel in-the oppositedirection of motion. In this prior art one end of the shock absorber isfixed to the vehicle while the other end engages the stop. Thisarrangement requires that individual shock absorbers be used for eachlimit of travel, thus necessitating the use of two shock absorbersrather than one. It is, therefore, an object of the present invention toprovide a shock absorber for a fixed path vehicle which is effective inboth directions of travel of the vehicle.

It is another object of the present invention to provide acylinder-piston type shock absorber in which the cylinder end of theshock absorber engages a fixed stop to limit travel in one direction andthe piston end of the shock absorber engages a fixed stop to limittravel in the opposite direction.

It is a further object of the present invention to provide a singlecontrol stop mechanism which will be effective to control decelerationrates at both ends of travel of the vehicle.

It is a further object of the present invention to provide an enclosedcylinder double-ended piston fluid shock absorber having a closed fluidcircuit with restricted flow of fluid permitted between one side and theother of said piston and in which the piston end of the device engages afixed stop to limit travel of a fixed path vehicle in one direction andthe cylinder end of the device engages a second stop to limit travel ofthe vehicle in the other direction.

Further objects of the present invention will become apparent uponinspection of the drawings and specifications and will be pointed out inthe claims.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENT Referring to the drawings:

FIG. I is a schematic view showing an automatic storage system in whichthe stacker is a fixed path vehicle utilizing the present invention;

FIG. 2 is a plan view of the base of a stacker vehicle using the presentinvention;

FIG. 3 is a vertical view of one side of FIG. 2 showing the presentinvention in greater detail;

FIG. 4 is a cross-section of the shock absorber device used in oneembodiment of the present invention.

Referring more particularly to FIG. 1, the bin structure 2 has a seriesof pairs of angle supports 4 and 6 capable of receiving pallets 8 from afixed path stacker vehicle 10 having an elevator 12 and a materialhandling lateral platform I4 which extends and retracts in and out ofthe bins formed by the angle iron supports 4 and 6.

The storage system includes a multiplicity of bins similar to 2 whichare separated by aisles l6, 18, etc. which have pairs of rails 20-22 onwhich the stack 10 travels in the aisle. The stacker I0 may betransferred from aisle to aisle by a transfer cart 24 having loadingstations 26 and 28 thereon. The rails 20 and 22 are extended onto thetransfer cart 24 so that the'stacker 10 may be driven onto the transfercart. To limit the movement of the stacker onto the transfer cart,positive stops 30 and 32 are located on the transfer cart, one on eachside of the extension of the rail 20, and stops 34 and 36 are similarlylocated, one on each side of the rail 22.v The members 30 and 32 act asa single stop, as do the members 34 and 36 and, of course, each of thesepairs in certain modifications of the invention may be combined as asingle stop member. Stops 40 and 42 straddle the rail 20 and the stops44 and 46 straddle the rail 22 to act as stops to limit the travel ofthe stacker in the direction away from the transfer cart. Here again 40and 42 may be combined into a single stop and 44 and 46 may also becombined into a single stop, since their mounting is optional and eachpair operates as single stops against a single cooperating shockabsorber means.

. The stacker 10 in the preferred embodiment of the present inventionhas two shock absorber means 48 and 50 (FIG. 1). One end of the shockabsorber means 48 engages the stop 44-46, and one end of the shockabsorber means 50 engages the stop 40-42, while the other end of thestops 48 and 50 engage the stacker to control the final decelerationrate as the stacker' is stopped at its limit of travel. When the fixedpath means 52 through wheels 54 and 56 on rails 20 and 22 in twodirections in the aisle 16. The shock absorbing. means 48 and 50 areidentical in construction and op-" eration, and 48 will be described indetail.

Referring now to FIGS. 2, 3 and 4, the shock ab sorber mechanism 48consists of a fluid cylinder 58' tached to the piston rod 60 is animpact block 64 and.

attached to the cylinder 58 is an impact block 62. The

spring 84 urges the piston 76 into the extended position thereby forcingthe block 64 into engagement with the bracket 66 and the block 62 intoengagement with the bracket 68, the brackets 66 and 68 are integralparts of the stacker and are welded to the side rails 70 and 72,

which in turn are part of the stacker vehicle frame. Side rails 70 and72 have guides 80 and 78, respectively, which carry the blocks 62 and 64so that the shock absorber assembly floats between the brackets 66 and68 and is held in place by the guides 78 and 80. The cavities 86 and 88are filled with shock absorber fluid and this fluid is forced betweenthe two cavities through the restricted opening 82 as the piston 76moves in the cylinder 58 during its shock absorber action while stoppingthe fixed path stacker vehicle 10. The shock absorber fluid, the size ofthe cylinder 58, the size of the piston 76, the size of the opening 82and the dimension of the spring 84 are all selected to give the properdeceleration rate for a particular weight vehicle.

If two or more shock absorber assemblies are used, such as illustratedin FIG. 2, they are normally so located and so designed as to giveuniform deceleration rates at each assembly. If two are used of equaldimensions, they are normally placed an equidistance each side of thecenter of mass of the vehicle. (This is illustrated in FIG. 2.)

A single floating shock absorber assembly aligned with the vehiclecenter of mass may be used if the construction of the vehicle sopermits.

OPERATION OF PREFERRED EMBODIMENT In one preferred embodiment, theinvention is used as illustrated in an automatic storage systemenvironment. In this case the stops 30-32 and 34-36 are so located onthe transfer car as to stop the stacker at the proper location on thetransfer car for its transportation between aisles, (for example,transporting from aisle 16 to 18). The stops 40-42 and 44-46 are locatedat the end of the aisle opposite the transfer car to limit the travel ofthe stacker in that direction. Should the stacker be driven down therails 20 and 22 into these latter stops limiting travel,- the members 62and 92 would be driven into the stops 44-46 and 40-42, respectively.This would drive the members 62 and 92 away from the brackets 68 and 96,respectively, and urge the members 64 and 94 against the brackets 66 and98, respectively.

Referring to the operation of the shock absorber 48 to which the shockabsorber 50 is identical, and to FIGS. 3 and 4, it will be seen that asthe member 62 leaves the bracket 68 the spring 84 is compressed, sincethe piston 76 is held from moving relative to the stacker 10 by member64 abutting member 66. Oil is then forced from the cavity 88 into thecavity 86 through the restrictive opening 82. The rate of decelerationis controlled by the rate of flow of fluid through the opening 82, whichrateof flow is dependent on the difference in fluid pressure in thecavity 88 over that in cavity 86. It may thus be seen that thedeceleration forces may be limited to a magnitude determined by thedesign parameters of the stacker and the shock absorber mechanism. Theenergy absorbed by forcing the oil through the restricted opening 82 andthe compression of the spring 84 gradually brings the stacker to a stopat which time the pressure between the chambers 86 and88 are stabilizedand equal. At this point the spring compression forces push the block 62back toward the bracket 68 and thus moves the stacker in the reversedirection until member 62 is in contact with the limit stop 44-46 andthe bracket 68, at which point there isnofurther movement.

When the stacker is moved in the reverse direction toward the transfercart to the limit of its travel, the member 64 engages the stops 34-36on the transfer cart and the shock absorbing mechanism 48 acts in thesame way as described above except the member 64 moves away from thebracket 66 compressing the spring thereby causing the transfer of theshock absorber fluid through the restricted opening 82. When the kineticenergy of the moving stacker is absorbed by the compression of thespring 84 and the transfer of the fluid from 88 to 86, the stackerstops. The spring then by its compression forces, forces the member 64back towards the member 66 until the stacker stops with the member 64 incontact with both the member 66 and the limit stop 34-36.

It may thus be seen that the present invention provides a controlleddeceleration positive stop means for flxed path vehicles, particularlyvehicles used as stackers in automatic storage systems. By properlyselecting the various elements of this disclosure, any desired rate ofdeceleration may be obtained for the stacker or other fixed pathvehicle.

The present invention provides a self-contained double-acting shockabsorber device which permits the use of one device for both directionsof operation into limit stops and thus reduces the initial cost andmaintenance costs of the device.

Having thus described the preferred embodiment of the present invention,it will, of course, be understood that various changes may be made inthe formed details, arrangement and proportion of the parts withoutdeparting from the scope of the invention which consists of the mattersshown and described herein as set forth in the appended claims.

We claim:

1. Material handling apparatus comprising:

a material transporting vehicle,

means for guiding said vehicle in a fixed path,

a first stop means located in said fixed path capable of limiting thedistance of movement of said vehicle in one direction of travel,

a second stop means located in said fixed path capable of limiting thedistance of movement of said vehicle in the opposite direction oftravel,

a floating shock absorbing mechanism carried by said materialtransporting vehicle and capable of engaging said first stop means whensaid vehicle is travelling in one direction to decelerate said vehicleto zero velocity at a desired rate, and capable of engaging said secondstop means when said vehicle is travelling in the opposite direction oftravel to decelerate said vehicle to zero velocity at the same desiredrate, the improvement wherein said shock absorbing mechanism comprisesfirst movable means defining a fluid chamber second movable meansincluding a piston in said chamber separating it into first and secondcavities, resilient means biasing said piston toward a referenceposition. a restricted opening in said piston providing bidirectionalfluid communication between said cavities, said mechanism beingslidably'mounted on said vehicle for sliding motion in the direction ofsaid path, one of said first and second movable means being aligned withthe stop means for either direction of travel and one said first andsecond means being aligned with a relatively fixed part of said vehiclefor either direction of travel,

3. Material handling apparatus as claimed in claim 1 in which,

said floating shock absorber mechanism consists of two shock absorberslocated equidistance on opposite side of the center of mass of saidmaterial transporting vehicle normal to its direction of travel, and

said first stop means consists of two stops simultaneously engaged bysaid two shock absorbing means when said material transporting vehicleis traveling in one direction to its limit of travel, and

said second stop means consists of two stops which are engagedsimultaneously by said two shock absorbing means, respectively, whensaid vehicle reaches its limit of operation in the opposite direction oftravel,

whereby said vehicle is stopped by exerting substantially equal forceson each of said shock absorbing means.

4. (Material handling apparatus as claimed in claim 1 in which:)Material handling apparatus comprising;

a material transporting vehicle,

means for guiding said vehicle in a fixed path,

a first stop means located in said fixed path capable of limiting thedistance of movement of said vehicle in one direction of travel,

a second stop means located in said fixed path capable of limiting thedistance of movement of said vehicle in the opposite direction oftravel,

a floating shock absorbing mechanism carried by said materialtransporting vehicle and capable of engaging said first stop means whensaid vehicle is travelling in one direction to decelerate said vehicleto zero velocity at a desired rate, and capable of engaging said secondstop means when said vehicle is travelling in the opposite direction oftravel to decelerate said vehicle to zero velocity at the same desiredrate, the improvement wherein said floating shock absorbing mechanismincludes a fluid cylinder assembly, and a piston assembly in which saidcylinder assembly has a cylinder head end and said piston assembly has apiston rod end, and

said cylinder head end engages the first of said (stops) stop meanswhile the piston rod end' engages said vehicle in one direction oftravel, and

said piston rod end engages the second of said (stops) stop means whilethe cylinder head end engages said vehicle in the opposite direction oftravel,

whereby fluid is forced out of said cavity formed by said cylinderandsaid piston to absorb energy and thereby decelerate said vehicle.

5. Material handling apparatus as claimed in claim 4 in which eachfloating shock absorber assembly includes: (a cylinder assembly having acylinder head end and a piston rod end, a piston assembly having apiston and piston rod,)

said piston fitted in said cylinder to produce a fluid cavity on eachside of said piston,

means for permitting restrictive flow of fluid between said cylinderhead end and said piston rod end on opposite sides of said piston,

whereby fluid is forced from one of said cavities to the other of saidcavities by (relevant) relative movement between said materialtransporting vehicle and said stop means.

6. Material handling apparatus as claimed in claim 4 including:

resilient biasing means between said piston assembly and ,said cylinderassembly to force said piston assembly and said cylinder assembly intoan extended position,

whereby said piston assembly is maintained in contact with one portionof said vehicle, and said cylinder assembly is maintained in contactwith another portion of said vehicle. 7

7. Material handling apparatus as claimed in claim 5 including:

resilient biasing means between said piston assembly and said cylinderassembly to force said piston assembly and said cylinder assembly intoan extended position,

whereby said piston assembly is maintained in contact with one portionof said vehicle, and said cylinder assembly is maintained in contactwith another portion of said vehicle.

8. Material handling apparatus for automatic storage system comprising:

a stacker,

two parallel floor mounted rails capable of supporting said stacker,

(four) two pairs of stops, (two) one pair being mounted adjacent (eachof) said rails and so located as to limit the travel of said stacker inone direction and another pair being mounted adjacent said rails and solocated as to limit the travel of the stacker in the other direction,

said stacker having four supporting wheels thereon capable of supportingsaid stacker on said rails,

two of said wheels spaced apart on each of said rails,

a floating shock absorbing device mounted in the space between each pairof wheels,

the improvement wherein; said. shock absorbing device comprises; firstmovable means defining a fluid chamber,

second movable means including a piston in said chamber separating itinto first and second cavities, resilient means biasing said pistontoward a reference position,

a restricted opening in said piston providing bidirectional fluidcommunication between said cavities, said device being slidably mountedon said vehicle for sliding motion in the direction of said path, one offirst and second movable means being aligned with the respective stopand one of said first and second movable means being aligned with arelatively fixed part of said vehicle for either direction of travel,

the first (end) movable means of each of said devices capable ofengaging a first pair of said stops while the second (end) movable meansof each of said devices engages said stacker to thereby stop themovement of said stacker in a first direction of movement,

the said second (end) movable means of each of said devices capable ofengaging a second pair of said stops while said first (end) movablemeans of each of said devices engages said stacker to thereby stop themovement of said stacker in a second direction of movement.

1. Material handling apparatus comprising: a material transportingvehicle, means for guiding said vehicle in a fixed path, a first stopmeans located in said fixed path capable of limiting the distance ofmovement of said vehicle in one direction of travel, a second stop meanslocated in said fixed path capable of limiting the distance of movementof said vehicle in the opposite direction of travel, a floating shockabsorbing mechanism carried by said material transporting vehicle andcapable of engaging said first stop means when said vehicle istravelling in one direction to decelerate said vehicle to zero velocityat a desired rate, and capable of engaging said second stop means whensaid vehicle is travelling in the opposite direction of travel todecelerate said vehicle to zero velocity at the same desired rate, theimprovement wherein said shock absorbing mechanism comprises firstmovable means defining a fluid chamber second movable means including apiston in said chamber separating it into first and second cavities,resilient means biasing said piston toward a reference position, arestricted opening in said piston providing bidirectional fluidcommunication between said cavities, said mechanism being slidablymounted on said vehicle for sliding motion in the direction of saidpath, one of said first and second movable means being aligned with thestop means for either direction of travel and one said first and secondmeans being aligned with a relatively fixed part of said vehicle foreither direction of travel, whereby said vehicle is (restricted tomovement between said stops and) decelerated to zero velocity (at eachlimit of movement) smoothly and without undue mechanical shock uponengagement of one of said first and second movable means with said stopmeans for either direction of travel.
 2. Material handling apparatus asclaimed in claim 1 in which, the means for guiding said vehicle in afixed path includes supporting rails.
 3. Material handling apparatus asclaimed in claim 1 in which, said floating shock absorber mechanismconsists of two shock absorbers located equidistance on opposite side ofthe center of mass of said material transporting vehicle normal to itsdirection of travel, and said first stop means consists of two stopssimultaneously engaged by said two shock absorbing means when saidmaterial transporting vehicle is traveling in one direction to its limitof travel, and said second stop means consists of two stops which areengaged simultaneously by said two shock absorbing means, respectively,when said vehicle reaches its limit of operation in the oppositedirection of travel, whereby said vehicle is stopped by exertingsubstantially equal forces on each of said shock absorbing means. 4.(Material handling apparatus as claimed in claim 1 in which:) Materialhandling apparatus comprising; a material transporting vehicle, meansfor guiding said vehicle in a fixed path, a first stop means located insaid fixed path capable of limiting the distance of movement of saidvehicle in one direction of travel, a second stop means located in saidfixed path capable of limiting the distance of movement of said vehiclein the opposite direction of travel, a floating shock absorbingmechanism carried by said material transporting vehicle and capable ofengaging said first stop means when said vehicle is travelling in onedirection to decelerate said vehicle to zero velocity at a desired rate,and capable of engaging said second stop means when said vehicle istravelling in the opposite direction of travel to decelerate saidvehicle to zero velocity at the same desired rate, the improvementwherein said floating shock absorbing mechanism includes a fluidcylinder assembly, and a piston assembly in which said cylinder assemblyhas a cylinder head end and said piston assembly has a piston rod end,and said cylinder head end engages the first of said (stops) stop meanswhile the piston rod end engages said vehicle in one direction oftravel, and said piston rod end engages the second of said (stops) stopmeans while the cylinder head end engages said vehicle in the oppositedirection of travel, whereby fluid is forced out of said cavity formedby said cylinder and said piston to absorb energy and thereby deceleratesaid vehicle.
 5. Material handling apparatus as claimed in claim 4 inwhich each floating shock absorber assembly includes: (a cylinderassembly having a cylinder head end and a piston rod end, a pistonassembly having a piston and piston rod,) said piston fitted in saidcylinder to produce a fluid cavity on each side of said piston, meansfor permitting restrictive flow of fluid between said cylinder head endand said piston rod end on opposite sides of said piston, whereby fluidis forced from one of said cavities to the other of said cavities by(relevant) relative movement between said material transporting vehicleand said stop means.
 6. Material handling apparatus as claimed in claim4 including: resilient biasing means between said piston assembly andsaid cylinder assembly to force said piston assembly and said cylinderassembly into an extended position, whereby said piston assembly ismaintained in contact with one portion of said vehicle, and saidcylinder assembly is maintained in contact with another portion of saidvehicle.
 7. Material handling apparatus as claimed in claim 5 including:resilient biasing means between said piston assembly and said cylinderassembly to force said piston assembly and said cylinder assembly intoan extended position, whereby said piston assembly is maintained incontact with one portion of said vehicle, and said cylinder assembly ismaintained in contact with another portion of said vehicle.
 8. Materialhandling apparatuS for automatic storage system comprising: a stacker,two parallel floor mounted rails capable of supporting said stacker,(four) two pairs of stops, (two) one pair being mounted adjacent (eachof) said rails and so located as to limit the travel of said stacker inone direction and another pair being mounted adjacent said rails and solocated as to limit the travel of the stacker in the other direction,said stacker having four supporting wheels thereon capable of supportingsaid stacker on said rails, two of said wheels spaced apart on each ofsaid rails, a floating shock absorbing device mounted in the spacebetween each pair of wheels, the improvement wherein; said shockabsorbing device comprises; first movable means defining a fluidchamber, second movable means including a piston in said chamberseparating it into first and second cavities, resilient means biasingsaid piston toward a reference position, a restricted opening in saidpiston providing bidirectional fluid communication between saidcavities, said device being slidably mounted on said vehicle for slidingmotion in the direction of said path, one of first and second movablemeans being aligned with the respective stop and one of said first andsecond movable means being aligned with a relatively fixed part of saidvehicle for either direction of travel, the first (end) movable means ofeach of said devices capable of engaging a first pair of said stopswhile the second (end) movable means of each of said devices engagessaid stacker to thereby stop the movement of said stacker in a firstdirection of movement, the said second (end) movable means of each ofsaid devices capable of engaging a second pair of said stops while saidfirst (end) movable means of each of said devices engages said stackerto thereby stop the movement of said stacker in a second direction ofmovement.